1. Field of the Invention
The present invention relates generally to a camera having a multi automatic focus adjusting system and a method of adjusting focus.
2. Description of the Related Art
An autofocus (AF) camera measures the distance from the camera to a lens either actively or passively. In the active mode, the camera emits light or ultrasonic waves toward the object, detects the returning waves from the object and then calculates the distance from the object based on the detected result. In the passive mode, under natural lighting, the camera receives light emitted or reflected from the object passively and determines whether the focus is correct using the contrast or the phase of the light,
Intermediate grade cameras commonly use active autofocus because the autofocus can be operated regardless of the light conditions and active autofocus has a lower expense. However, active autofocus may operate incorrectly if a reflecting surface such as a window is in front of the object. The emitted ultrared rays or ultrasonic waves can not transmit the window and the camera will focus incorrectly. Further, with known active autofocus systems, only the center positioned object is in focus and the surrounding scenery or character is photographed vaguely.
A camera system using active autofocus emits single light from a light emitting element/detects light reflected off of the object, measures the distance from the object based upon the reflected light, and then adjusts the focus. In that event, focus is only measured to center positioned objects, and not completely clear photographs are obtained.
To solve the above-mentioned problems, a multi automatic focus controlling system may be used in the camera. In such a system, the camera adjusts the focus automatically with respect to the entire object including the surrounding objects as well as the center positioned object in accordance with a plurality of light or ultrasonic waves detected by a plurality of light receiving elements.
U.S. Pat. No. 4,800,409, entitled "Control Device For Use In A Camera Having An Objective Lens," discloses a multi automatic focus controlling system which measures the distance from the object based on light emitted from a light emitting element and reflected off of the object, calculates a suitable AF step based on the above measuring result, and, if the interval of the AF step in accordance with each measured distance from the object is within one step, produces an AF step signal in accordance with the AF step stored in a first memorizing means.
U.S. Pat. No. 5,151,883, entitled "Focus Adjustment Device Having Restricting Means For Restricting A Selecting Action According To The Degree Of Nearness Of A Distance Measurement," discloses a camera in which the AF step is set up in accordance with the measured distance from an object which is the nearest object next to the central positioned object with respect to the camera when the measured distance from the central positioned object is smaller than the predetermined value, i.e., the central positioned object is too near the camera.
These cameras also have a disadvantage in that objects at different distances can not be photographed clearly because the cameras select information simply and perform the AF calculation based on the selected information.